Dampener control system for lithographic printing press

ABSTRACT

A dampening system for a lithographic printing press which has a plurality of feed motors for controlling the rate at which dampening fluid is supplied to the printing plate in the press. The system includes a tachometer generator for producing an electrical signal representing the press speed, and means for converting the electrical signal to a mechanical displacement. The mechanical displacement is applied to a resistor matrix which produces a second electrical signal which represents a predetermined non-linear function of the press speed, with the particular nature of the function being determined by the setting of the resistor matrix. This second electrical signal is supplied to the speed control means associated with the feed motors so as to automatically vary the speed of the feed motors according to the predetermined non-linear function of the press speed.

United States Patent Rouse DAMPENER CONTROL SYSTEM FOR LITHOGRAPHIC PRINTING PRESS lnventor:

[72] William H. Rouse, Downers Grove,

Ill.

Assignee: North American Rockwell Corpora- I tion, Pittsburgh, Pa.

Filed: March 8, 1971 Appl. N0.: 121,875

US. CL ..3l8/77, 337/68 Int. Cl. ..H02p 5/46 Field of Search ..lOl/l48; 318/68, 77, 79, 80,

References Cited UNITED STATES PATENTS 11/1968 Hermachetal..l..i...l.l01/148 FOREIGN PATENTS OR APPLICATIONS 715,149 9/1954 Great Britain ..318/68 WIS/ 70 SERVO 4MP! lF/ER c. Aha/Fla? [45.1 Oct. 24-, 1972 Primary Examiner- -Bemard A. Gilheany AssistantExaminer--F. E. Bell Att0rney-Bronaugh, Dunbar, Levison, OConnor & Speer [57] ABSTRACT A dampening system for a lithographic printing press which has a plurality of feed motors for controlling the rate at which dampening fluid is supplied to the printing plate in the press. The system includes a tachome- 'ter generator for producing an electrical signal representing the press speed, and means-for converting the electrical signal to a mechanical displacement. The mechanical displacement is applied to a resistor matrix which produces a second electrical signal which represents a predetermined nonlinear function of the press speed, with the particular nature of the function being determined by the setting of the resistor matrix. This second electrical signal is supplied to the speed control means associated with the feed motors so as to automatically vary the speed of the feed motors according to the predetermined nonlinear function of the press speed.

4 Claims, 5 Drawing Figures 1 DAMPENER CONTROL SYSTEM FOR LITHOGRAPHIC PRINTING PRESS DESCRIPTION OF THE INVENTION The present invention relates generally to dampening systems for lithographic printing presses and, more particularly, to an improved dampening system which auby those familiar with this-art, the speed at which the feed motors are operated controls the rate at which ditives used in the art or any equivalent ink-repelling I liquid. The water is applied to specified areas of the plate surface in varying amounts from a form roller made of resilient material and receives water from a feed roller driven by a feed motor. Much time and effort has been expended in the past to regulate the feeding of the water in order to supply the moisture at a desired rate.

It is a primary object of the invention to provide an 1 improved dampening system which relates the rate of application of the dampening water to the press speed.

It is a further object of this invention to provide an improved dampening system of the foregoing type which is extremely reliable in operation.

Yet another object of this invention is to provide such an improved dampening system which can be economically manufactured and installed.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and 'upon reference to the drawings in which:

FIGS. la and lb form a single schematic diagram of a dampening control system embodying the present invention;

FIG. 2 is a graphical illustration of one exemplary non-linear function of press speed according to which the water supply rate is varied by the system of FIG. 1;

FIG. 3 is a graphical illustration of the biasing effect of the control system of FIG. 1 as applied to the function of FIG. 2; and

FIG. 4 is a graphical illustration of an adjustment of the slope of the function of FIG. 2, as effected by the control'system of FIG. 1.

While the invention will be described in connection with a certain preferred embodiment, it will be un-' derstood that it is not intended to limit the invention to the particular embodiment shown but, on the contrary, it is intended to cover the various alternatives and equivalent arrangements included within the spirit and scope of the invention.

' Turning now to the drawings and referring first to FIG. 1, the illustrative control system is provided for controlling the speed of a plurality of feed motors 10 which are included as conventional parts of standard dampening system'for lithographic printing presses. One example of such a dampening system is described in detail in U.S. Pat. No. 3,411,441, issued Nov. 19, 1968 to C. J. Hermach et al., and assigned to the as signee of the present invention. As is well understood the dampening water is fed to the printingplate. g In accordance with the present invention, the automatic control system includes first generating means for producing a first control signal representing the press speed, second generating means responsive to the first signal for producing a second control signal representing a predetermined non-linear function of the press speed, and control means responsive. to the second control signal for controlling the speed of the feed motors according to the predetermined non-linear function of the pressspeed. Thus, in the illustrative system, a tachometer. generator 11 is driven by the press so as to produce an electrical output signal directlyproportional to the press speed. This output [signal is scaled by a voltage divider comprising resistors 12 and 13, and the scaled output is applied via a potentiometer 14 to the input of a servo amplifier 15. The power input to the amplifier 15 is supplied from a d-c power supply 16. As an alternative to the tachometer generator 11, the signal proportional to press speed maybe generated by an auxiliary potentiometer having its wiper driven by the pilot motor in the main controller for the press. I

For the purpose of converting the electrical signal representing press speed to a mechanical displacement, the output of the amplifier 15 is applied to a position servo motor 17, the mechanical output of which is fed back to position the wiper of the.potentiometer 14.

Consequently, .itcan be seen that the amplifier 15 drives the position servo motor 17 until the position feedback signal from the motor output has adjusted the wiper of the potentiometer 14 to a point where the input voltage to the amplifier 15 is zero. At this point, both the output shaft of the position servo motor 17 and the wiper of the potentiometer 14 are displaced from their original positions by distances proportional to the press speed, thereby providing a mechanical output signal proportional to press speed.

In keeping with the present invention, the mechanical Output signal from the position servo motor 17, which is proportional to press speed, is applied to the input of a resistor matrix which is preset to producean electrical output signal representing a predetermined non-linear function of the mechanical input signal representing press speed. More specifically, the mechanical output from the position servo motor 17 adjusts the wiper of an input potentiometer 18 comprising one part of a resistor matrix 19. This resistor matrix 19 is a conventional component which is commercially available, such as the Vernistat resistor matrix manufactured by Perkin-Elmer Corporation. The resistor matrix 19 can be preset so that it responds to any given mechanical input, applied to the wiper of the input potentiometer 18, to produce an electrical output signal which varies according to the settings of a multiplicity of cross bar connectors 20 which connect the input potentiometer 18 to an output potentiometer 21. I

' More specifically, the adjustable cross bar connectors 20 connect a multiplicity of vertical bars 20a, which are electrically connected to the input potentiometer 18 at equally spaced intervals, to a corresponding multiplicity of horizontal bars 2012, which are electrically connected to the output potentiometer 21 at equally mechanical input to the wiper of potentiometer 18. For

example, the resistor matrix is typically set so that the electrical output signal across leads 22 and 23 varies according to the non-linear function illustrated graphically in FIG. 2, which is a hyperbola within an asymptote initially positive and sloped positively.

In accordance with one particular aspect of the invention, a manually adjustable control means is operatively connected to the resistor matrix 19 for changing the slope of the function generated by the matrix 19. Thus, a potentiometer 19a is connected to one end 'of the output potentiometer 21 for controlling the voltage level across the potentiometer 21. By adjusting the wiper on the potentiometer 19a, the press operator may change the slope of the function determined by the settings of the cross bar connectors 20 in the matrix 19, e. g., as illustrated graphically in FIG. 4.

In the illustrative system, the electrical output signal on leads 22 and 23 is supplied to the input of an a-c amplifier 24 for the purpose of re-scaling the output signal from the resistor matrix 19 to match that output signal to the following portion of the system. The a-c input to this amplifier 24 is obtained from an a-c power supply 25. The a-c output from the amplifier 24 is rectified by a diode bridge 26 and fed back to the input of the amplifier 24, via a potentiometer 27, a resistor 28 and a capacitor 29 for the purpose of stabilizing the amplifier.

The a-c output from the amplifier 24, which of course represents the function generated by the matrix 19, is also applied across the primary winding 30a of a transformerwhich biases the signal to a predetermined level as illustrated in FIG. 3. The purpose of this bias is to provide an operator modification of the signal supplied to the primary windings 31a, 32a, 33a, and 34a of a series of input transformers associated with the four corresponding feed motors 10. Thus, the signal from the secondary windings 30b and 30c associated with the primary winding 3011, as represented by the broken line in FIG. 3, is applied to modify the signal applied to the aforementioned primary windings 31a, 32a, 33a, and 34a connected in parallel with each other.

In order to automatically increase the signal across the primary windings 31a-34a in response to a change in press speed, the press speed control unit 35, which is a conventional part of most lithographic printing presses, energizes a relay 36 whenever either the faster" contacts 35a or the slower contacts 35b are closed, i.e., whenever the press speed is either increasing or decreasing. When the relay 36 is energized, it

opens a pair of normally closed contacts 36a and closes returns to thenormal open position, thereby de-energizing the relay 36 to close contacts 36a and open contacts 36b.

In the event that the operator wishes to manually adjust the water feed rate, he may manually adjust the bias effected by the biasing transformer by moving the tap on the secondary coil 30c. The knob for effecting displacement of the adjustable tap on the secondary winding 300 is preferably mounted on the main press control panel so that it is readily accessible to the press operator.

The systems for controlling the speed of operation of the feed motors- 10 in response to the signals applied to the primary windings 31a, 32a, 33a, and 34a are conventional and well known in the art and, therefore, need not be described in detail herein. It should suffice to state that the secondary windings 31b, 32b, 33b, and 34b associated with the corresponding primary windings 31a-34a are connected across respective diode bridges 37, 38, 39, and 40, and the resulting rectified signals are applied to corresponding potentiometers 41, 42, 43, and 44. These potentiometers 41-44 may be manually adjusted to control the speed of each individual feed motor 10 according to the amount of water needed for a particular ink or particular web width during any given press run. From the potentiometers 4144, corresponding input signals are supplied to the conventional speed control units 45, 46,

47, and 48 associated with the four feed motors 10.

As can be seen from the foregoing detailed description, the present invention provides an improved lithographic press dampening system which controls the rate of supply of the dampening'water in a completely automatic manner, and more accurately than dampening systems proposed heretofore. This improved dampening system is extremely reliable in operation, and yet can be economically manufactured, installed and maintained.

I claim as my invention:

1. In combination with a lithographic printing press unit having a variable speed rotary printing plate and variable speed feed motor means controlling the rate at which dampening fluid is supplied to said printing plate, control means comprising:

first. means operationally coupled to said variable speed rotary printing plate and developing a first means output that is a linear function of the speed of said rotary printing plate;

second means operationally coupled to said first means to receive said first means output and developing a second means output in response thereto that a non-linear function of the speed of said rotary printing plate; and

motor control means operationally coupled to said second means and to said feed motor means to receive said second means output and to control the speed of said feed motor means linearly in response to said second means output; said non-linear function being a hyperbola-like function which approaches an asymptote with increased rotary printing plate speed and increased feed motor means speed.

2. The invention defined by claim 1 wherein said second means output is an electrical signal having a voltage which varies according to said non-linear funcbeing varied to change the rate at which said hyperbola-like function approaches an asymptote with. in-' creased rotary printing plate speed and increased feed motor means speed.

4.,The invention defined by claim 1 wherein said second means output is an electrical signal having a voltage which varies according to said non-linear function, said second means comprising a first resistor means developing avoltage that varies according to said non-linear function and a second means that develops a bias voltage that is combined with said first resistor means voltage. 

1. In combination with a lithographic printing press unit having a variable speed rotary printing plate and variable speed feed motor means controlling the rate at which dampening fluid is supplied to said printing plate, control means comprising: first means operationally coupled to said variable speed rotary printing plate and developing a first means output that is a linear function of the speed of said rotary printing plate; second means operationally coupled to said first means to receive said first means output and developing a second means output in response thereto that a non-linear function of the speed of said rotary printing plate; and motor control means operationally coupled to said second means and to said feed motor means to receive said second means output and to control the speed of said feed motor means linearly in response to said second means output; said non-linear function being a hyperbola-like function which approaches an asymptote with increased rotary printing plate speed and increased feed motor means speed.
 2. The invention defined by claim 1 wherein said second means output is an electrical signal having a voltage which varies according to said non-linear function, said second means comprising a resistor matrix having an input potentiometer means with cooperating wiper element, said wiper element being moved in response to said first means output.
 3. The invention defined by claim 1 wherein said second means output is an electrical signal having a voltage which varies according to said non-linear function, said second means comprising a variable first resistor element and a cooperating variable second resistor element which varies in resistance according to said non-linear function, said first resistor element being varied to change the rate at which said hyperbola-like function approaches an asymptote with increased rotary printing plate speed and increased feed motor means speed.
 4. The invention defined by claim 1 wherein said second means output is an electrical signal having a voltage which varies according to said non-linear function, said second means comprising a first resistor means developing a voltage that varies according to said non-linear function and a second means that develops a bias voltage that is combined with said first resistor means voltage. 